Orbit attitude control device, and method of controlling orbit attitude

ABSTRACT

An orbit attitude control device includes a plurality of nozzles for injecting combustion gas supplied from a combustion chamber, and a control section configured to calculate nozzle opening degree correction values so that a deviation between a detection value of the pressure of the combustion chamber and a command value becomes smaller. The control section is configured to calculate a total correction value so that the deviation between the detection value and the command values becomes smaller. A total value T1 for first group nozzles and a total value T2 for second group nozzles are calculated. The total correction value is distributed to the opening degree correction values for the first group nozzles with a ratio of T2/(T1+T2) and to the opening degree correction values for the second group nozzles with a ratio of T1/(T1+T2).

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2012-260151, filed on Nov. 28, 2012, thedisclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The present invention rerates to a technique for controlling an orbit ofa flying object.

BACKGROUND ART

Technologies for controlling an attitude or orbit of a flying objectflying through space or the atmosphere have been developed. In a systemtypically called DACS (Divert and Attitude Control System), an attitudecontrol thruster for controlling an attitude of the flying object and anorbit control thruster for changing an orbit are used for controllingthe attitude and orbit.

Patent Literature 1 discloses one example of a thruster control method.The method includes: detecting a pressure of a combustion chamber,comparing the detected pressure with a predetermined pressure value, andchanging discharge areas of a plurality of nozzles for substantiallysame amount so that the pressure of the combustion chamber becomes thepredetermined pressure, based on a difference between the detectedpressure and the predetermined pressure.

CITATION LIST

[Patent literature 1] U.S. Pat. No. 5,456,425

SUMMARY OF THE INVENTION

A combustion gas is supplied to a plurality of nozzles included in athruster from a common combustion chamber. The each nozzle includes avalve which is controlled based on a designated opening degree commandvalue. Each nozzle injects the combustion gas with an amountcorresponding to the opening degree, and thereby an orbit attitude ofthe flying object is controlled.

A pressure of the combustion chamber for supplying the combustion gas ofthe thruster is desirably kept constant. Accordingly, the opening degreeof the valve of the nozzle is controlled so that the pressure of thecombustion chamber is kept constant. However, in fact, when the openingdegree command value is inputted so as to keep the pressure of thecombustion chamber constant, there is a case where the pressure of thecombustion chamber changes unpredictably because of various disruptingfactors. As such disrupting factors, a mechanical accidental error,thermal expansion of the valve or the like, and ununiformity of a fuelor the like are considered. It is expected that the pressure of thecombustion chamber is controlled to be kept constant in order tomaintain stable combustion.

Moreover, when operation amounts are largely biased in a plurality ofnozzles included in the thruster, conditions of nozzles are easilyvaried. Accordingly, it is desired that the nozzles are evenly used.

An orbit attitude control device according to the present inventionincludes: a plurality of nozzles configured to inject a combustion gassupplied from a combustion chamber, wherein opening degrees of theplurality of nozzles are configured to be controlled in response toopening degree command values; and a control section configured tocalculate nozzle opening degree correction values that are correctionvalues for opening degree command values of the plurality of nozzles sothat a deviation between a detection value of a pressure of thecombustion chamber and a command value of the pressure becomes smaller,and correct the opening degree command values by the nozzle openingdegree correction values. A first group nozzles belonging to a firstgroup of the plurality of nozzles are configured to inject combustiongas in opposite directions along a first axis, and a second groupnozzles belonging to a second group of the plurality of nozzles areconfigured to inject combustion gas in opposite directions along asecond axis. The control section is configured to calculate a totalcorrection value that is a correction value for a total value of theopening degree command values of the plurality of nozzles so that thedeviation between the detection value of the pressure and the commandvalue of the pressure becomes smaller, calculate a total first groupopening degree value T1 that is a total value of the opening degreecommand values of the first group nozzles, and a total second groupopening degree value T2 that is a total value of the opening degreecommand values of the second group nozzles, distribute the totalcorrection value into the first group opening degree correction valuewith a ratio of T2/(T1+T2) and into the second group opening degreecorrection value with a ratio of T1/(T1+T2), calculate the nozzleopening degree correction values for the first group nozzles so that atotal value becomes the first group opening degree correction value, andcalculate the nozzle opening degree correction values for the secondgroup nozzles so that a total value becomes the second group openingdegree correction value.

A method of controlling an orbit attitude according to the presentinvention includes: inputting opening degree command values for openingdegrees of a plurality of nozzles which inject a combustion gas suppliedfrom a combustion chamber; calculating nozzle opening degree correctionvalues that are correction values for opening degree command values ofthe plurality of nozzles so that a deviation between a detection valueof a pressure of the combustion chamber and a command value of thepressure becomes smaller; and calculating the nozzle opening degreecorrection values for the plurality of nozzles based on the openingdegree command values to correct the opening degree command values bythe nozzle opening degree correction values. A first group nozzlesbelonging to a first group of the plurality of nozzles are configured toinject combustion gas in opposite directions along a first axis, and asecond group nozzles belonging to a second group of the plurality ofnozzles are configured to inject combustion gas in opposite directionsalong a second axis. The calculating nozzle opening degree correctionvalues includes: calculating a total correction value that is acorrection value for a total value of the opening degree command valuesof the plurality of nozzles so that the deviation between the detectionvalue of the pressure and the command value of the pressure becomessmaller; calculating a total first group value T1 that is a total valueof the opening degree command values of the first group nozzles, and atotal second group value T2 that is a total value of the opening degreecommand values of the second group nozzles; distributing the totalcorrection value into the first group correction value and the secondgroup correction value based on a ratio of the total first group valueand the total second group value; calculating the nozzle opening degreecorrection values for the first group nozzles so that a total valuebecomes the first group correction value; and calculating the nozzleopening degree correction values for the second group nozzles so that atotal value becomes the second group correction value.

According to the present invention, an orbit attitude control device anda method of controlling an orbit attitude can be provided, which areable to control the thruster with keeping the pressure of the combustionchamber constant. Moreover, according to the present invention, an orbitattitude control device and a method of controlling an orbit attitudeare provided, which are able to suppress a variation in operationamounts of the plurality of nozzles.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a sectional view showing an attitude control device;

FIG. 1B is a graph indicating a relationship between an angle of avalving element and a throat area;

FIG. 2A is a sectional view showing a divert thruster;

FIG. 2B is a graph indicating a relationship between a location of avalving element and a throat area;

FIG. 3 is a diagram for explaining distribution of opening degrees inthe divert thruster;

FIG. 4A is a diagram showing a distribution of opening degrees to pintlevalves when a total opening degree command value is changed in thedivert thruster;

FIG. 4B is a diagram showing a distribution of opening degrees to pintlevalves when a total opening degree command value is changed in thedivert thruster;

FIG. 5A is a diagram showing a distribution of opening degrees to pintlevalves when a total opening degree command value is changed in thedivert thruster;

FIG. 5B is a diagram showing a distribution of opening degrees to pintlevalves when a total opening degree command value is changed in thedivert thruster;

FIG. 6 is a diagram for explaining an operation of a control section;and

FIG. 7 is a diagram for explaining an operation of a control section.

DESCRIPTION OF EMBODIMENTS

[Configuration of a Thruster]

With reference to the drawings, embodiments will be described. FIG. 1Ais a cross-sectional view showing an attitude control device accordingto the present embodiment. A flying object including this attitudecontrol device has an outer shape which is almost symmetrical to thex-axis illustrated in the drawing, and is propelled roughly along thex-axis direction. FIG. 2A is a sectional view showing A-A cross-sectionof a divert thruster 8 of FIG. 1A.

A solid fuel 4 is arranged inside a main body 2 of the attitude controldevice. When the flying object flies, the solid fuel 4 combusts and acombustion chamber 6 inside the main body 2 is filled with combustiongas. An internal pressure of the combustion chamber 6 is detected by acombustion pressure sensor 7. A relatively small part of the combustiongas is supplied to an attitude control thruster 10. The attitude controlthruster 10 includes a plurality of nozzles which face to radialdirections of a cylindrical coordinate system whose center is the x-axis(a directions in YZ-plane whose start points are arranged on the x-axisin FIG. 1A). Each of the plurality of nozzles includes a rotary valve12. An opening degree of the rotary valve 12 is controlled by anelectrical signal. The combustion gas supplied to the attitude controlthruster 10 is injected from the each nozzle for an amount correspondingto the opening degree of the rotary valve 12, and thereby the attitudeof the flying object is controlled. A shape 14 of an opening portion ofthe rotary valve 12 is indicated in a lower right part of FIG. 1A. FIG.1B shows a graph indicating a relationship between an angle of a valvingelement and a throat area of the rotary valve 12.

A relatively large part of the combustion gas of the combustion chamber6 is supplied to the divert thruster 8. The divert thruster 8 includes aplurality of nozzles 15-1 to 15-4 which face to radial directions of thecylindrical coordinate system whose center is the x-axis (directions inYZ-plane whose start points are arranged on the x-axis in FIG. 1A). Theplurality of nozzles 15-1 to 15-4 includes pintle valves 16-1 to 16-4,respectively.

Opening degree command values concerning the pintle valves 16-1 to 16-4are provided, based on a wireless communication with an outside of theflying object or data stored in a storage device included in the flyingobject. A control section 17 controls actuators 18, based on the openingdegree command values and a detection value of a pressure of thecombustion chamber 6 which is detected by the combustion pressure sensor7. The actuators 18 control opening degrees of the pintle valves 16-1 to16-4. The combustion gas supplied to the divert thruster 8 is injectedfrom the each of the nozzles 15-1 to 15-4 for an amount corresponding tothe opening degrees of the pintle valves 16-1 to 16-4, and thereby theattitude of the flying object is controlled. A shape of an openingportion of the each of the pintle valves 16-1 to 16-4 is indicated in alower right part of FIG. 2A. FIG. 2B is a graph indicating arelationship between location of a valving element and a throat area ofthe each of pintle valves 16-1 to 16-4.

With reference to FIG. 3, a method of distributing opening degrees ofthe divert thruster 8 will be explained, which is a basis of the presentembodiment. When the solid fuel 4 stably combusts, a generation amountof the generated combustion gas in a unit of time is substantiallyconstant. Accordingly, a flow rate of the combustion gas supplied to theoutside from the combustion chamber 6 is desirably kept constant. Inparticular, it is desired that a flow rate of the combustion gasinjected from the divert thruster 8 whose injection amount is large iskept constant. Therefore, the opening degree of the each pintle valve iscontrolled so that a total of throat areas of the pintle valves 16-1 to16-4 included in the divert thruster 8 is a constant (this constantvalue is assumed to be 100%). The combustion pressure of the combustionchamber 6 is kept constant by such control, and a transitive fluctuationof the combustion pressure is suppressed.

FIG. 3(a) to (d) shows four pintle valves 16-1 to 16-4, respectivepercentages of throat areas, and a resultant force by injections fromthe pintle valves 16-1 to 16-4. As shown in FIG. 3(a), when the openingdegree of the pintle valve 16-1 is 100% and the pintle valves 16-2 to16-4 are fully closed, the resultant force acts along an upper directionin the drawing (the negative direction along the z-axis) and the orbitof the flying object is changed to be opposite direction of theresultant force. As shown in FIG. 3(b), when the opening degree of theeach of pintle valves 16-1 and 16-2 is 50% and the pintle valves 16-3and 16-4 are fully closed, the resultant force acts along an upper rightdirection and the orbit of the flying object is changed to be oppositedirection of the resultant force. When the resultant force by theinjection of the divert thruster is required to be reduced, as shownFIG. 3(c), a pintle valve facing to one direction and a pintle valvefacing to the opposite direction are simultaneously opened. For example,in FIG. 3(c), the pintle valve 16-3 facing to the positive directionalong the z-axis is opened with opening degree of 10%, and the pintlevalve 16-1 facing to the negative direction along the z-axis is openedwith opening degree of 60%. As a result, a force is obtained, which isequal to a resultant force that is obtained when the pintle valve facingto the negative direction along the z-axis is opened with opening degreeof 50%. If the orbit is not to be changed by the divert thruster 8, asshown in FIG. 3(d), in the pintle valves 16-1 to 16-4, the pintle valvesfacing to each other are set to be same opening degree.

Reference Example

When the pintle valves 16-1 to 16-4 are controlled by a fixed totalopening degree command value, the combustion pressure of the combustionchamber 6 does not necessarily become constant, because of disturbingfactors such as mechanical errors, thermal expansions of valves or thelike, and ununiformity of the fuel and so on. Accordingly, feed backcontrol for total opening degree of the divert thruster 8 is carried outby using the detection value of the combustion pressure sensor 7, sothat the pressure of the combustion chamber 6 becomes constant.

FIGS. 4A and 4B show an example of control in a case where the detectionvalue of the pressure of the combustion chamber 6 is smaller than a setvalue and the total opening degree of the divert thruster 8 iscontrolled to be reduced. By reducing the total opening degree, aninjection amount of the combustion gas is reduced, and the pressure ofthe combustion chamber 6 increases.

FIG. 4A indicates a case where the total opening degree command value ofthe divert thruster 8 is 100%, 70% of it is distributed to the pintlevalve 16-1, and 10% of it is distributed to each of the pintle valves16-2 to 16-4. At this state, it is assumed that the detection value ofthe pressure of the combustion chamber 6 is smaller than the set valueand the total opening degree command value is changed to be 90% byaddition of a total correction value of −10%. In this example, the totalcorrection value is evenly distributed to all pintle values 16-1 to16-4. As shown in FIG. 4B, by evenly distributing the total correctionvalue of −10% to the all pintle valves 16-1 to 16-4, the pressure of thecombustion chamber 6 is increased, keeping the direction of theresultant force the same.

On the contrary, when the detection value of the pressure of thecombustion chamber 6 is larger than the set value and the total openingdegree of the divert thruster 8 is controlled to be increased, apositive total correction value is added (the total opening degree isincreased) and the injection amount of the combustion gas increases todecrease the pressure of the combustion chamber 6. In this case, bychanging a symbol of the correction value for the opening degree of thepintle valve (−2.5% in FIG. 4B) to be opposite, the pressure of thecombustion chamber can be controlled to be kept constant.

Embodiment

Next, an embodiment according to the present invention will beexplained. FIGS. 5A and 5B show an example of control in a case wherethe detection value of the pressure of the combustion chamber 6 shiftsfrom the set value and the total opening degree of the divert thruster 8is controlled to be changed. FIG. 5A shows a case where the totalopening degree command value of the divert thruster 8 is 100%, 70% of itis distributed to the pintle valve 16-1, and 10% of it is distributed toeach of the pintle valves 16-2 to 16-4. At this state, a case is shownin FIG. 5B where the detection value of the pressure of the combustionchamber 6 becomes larger than the set value and the total opening degreecommand value is changed to be 110%.

In this example, nozzles facing to opposite directions are referred as anozzle group. For example, the nozzles 16-1 and 16-3 facing to oppositedirections are referred as a first nozzle group, and the nozzles 16-2and 16-4 facing to opposite directions are referred to as a secondnozzle group. In the same nozzle group, the opening degree correctionvalues are distributed to the nozzles with a same ratio.

In FIG. 5A, a total value T1 of the opening degree command values forthe first nozzle group is “70+10=80%”, and a total value T2 of theopening degree command values for the second nozzle group is“10+10=20%”. In this case, the total correction value “10%” isdistributed to the first nozzle group with a ratio of T2/(T1+T2), and tothe second nozzle group with a ratio of T1/(T1+T2). Accordingly, in theexample shown in FIG. 5A, the total correction value is distributed tothe first nozzle group by 2%, and to the second nozzle group by 8%. Thecorrection value is evenly distributed into the nozzles of the firstgroup 16-1, 16-3, the correction value is evenly distributed into thenozzles of the second group 16-2, 16-4, and thereby the correctionvalues shown in FIG. 5B are obtained.

According to such control, when the combustion pressure becomes largerthan the set value, the total correction value for the combustion gas isevenly distributed in opposite directions without changing the orbit.Moreover, the total correction value is largely distributed to a nozzlegroup having small opening degree command values. Accordingly, theopening degrees of the pintle valves 16-1 to 16-4 after the correctionare more even than those before the correction. The plurality of nozzles15-1 to 15-4 of the divert thruster 8 are desirably used evenly ratherthan used disproportionately. According to control shown in FIGS. 5A and5B, such more evenly-used control can be attained.

FIG. 6 shows a configuration of a control section 17 for realizing theabove mentioned control. Opening degree commands A1c to A4c for thepintle valves 16-1 to 16-4 are inputted into the control section 17,based on a wireless communication or data stored in a storage section.These values are corrected by correction values ΔA1 to ΔA4 for theopening degree commands of the pintle valves 16-1 to 16-4, respectively.The control section 17 outputs the corrected opening degree commands torespective actuators 18-1 to 18-4 of the pintle valves 16-1 to 16-4. Theactuators 18-1 to 18-4 drive, opening areas of the pintle valves 16-1 to16-4 are respectively set to be A1 to A4, and a total opening area At isdetermined. Following thrust forces are obtained by injection from eachof the nozzles 15-1 to 15-4.F1=Pc·A1·CfF2=Pc·A2·CfF3=Pc·A3·CfF4=Pc·A4·Cf

The Pc indicates the pressure of the combustion chamber 6, and Cfindicates a thrust coefficient. A thrust force along the z-axisdirection is determined by a difference between F1 and F3. A thrustforce along the y-axis direction is determined by a difference betweenF2 and F4.

The Pressure Pc of the combustion chamber 6 is detected by thecombustion pressure sensor 7. A calculator provided in the controlsection 17 calculates a total correction value ΔAt that is a correctionvalue for the total opening area At, based on a deviation ΔPc betweenthe detected pressure Pc and a combustion pressure target value Pcomwhich is provided by data stored in the storage section, in order tocarry out feed back control that is typically PID control.

The calculator of the control section 17 distributes the totalcorrection value ΔAt to the correction values ΔA1 to ΔA4 for the pintlevalves 16-1 to 16-4. This distribution is carried out according to thefollowing formulas.ΔA1=ΔA _(t)×(A2_(c) +A4_(c))/{2×(A1_(c) +A2_(c) +A3_(c) +A4_(c))}ΔA2=ΔA _(t)×(A1_(c) +A3_(c))/{2×(A1_(c) +A2_(c) +A3_(c) +A4_(c))}ΔA3=ΔA _(t)×(A2_(c) +A4_(c))/{2×(A1₀ +A2_(c) +A3_(c) +A4_(c))}ΔA4=ΔA _(t)×(A1_(c) +A3_(c))/{2×(A1_(c) +A2_(c) +A3_(c) +A4_(c))}

By using these correction values as the correction values for theopening degree commands A1c to A4c for the pintle valves 16-1 to 16-4,the total opening degree correction value is largely distributed into anozzle group having small opening degree command values, and thepressure of the combustion chamber 6 is kept constant.

[Control of Correcting the Opening Degree by a Measurement Value ofAcceleration]

As mentioned above, the example was explained in a case where the divertthruster is controlled in response to a change of the pressure in thecombustion chamber. On the other hand, in order that the flying objectaccurately flies along an orbit according to commands, feed back controlusing a measurement value of acceleration of the flying object isdesired. FIG. 7 shows an example of such control.

The orbit attitude control device includes an acceleration sensorsection. The acceleration sensor section includes a y-axis accelerationsensor for measuring acceleration in the y-axis direction of thecoordinate axes illustrated in FIG. 1A and FIG. 2A, and a z-axisacceleration sensor for measuring acceleration in the z-axis direction.

Respective opening degree commands A1c to A4c for each of the pintlevalves 16-1 to 16-4 are inputted into the control section 17, by awireless communication or based on data stored in a storage section.These values are corrected by correction values ΔA1 to ΔA4 for theopening degree commands of the respective pintle values 16-1 to 16-4.The control section 17 outputs the corrected opening degree commands torespective actuators 18-1 to 18-4 of the pintle valves 16-1 to 16-4.Actuators 18-1 to 18-4 drive, the opening areas of the pintle valves16-1 to 16-4 are respectively set to be A1 to A4, and the total openingarea At is determined. The following thrust forces are obtained by theinjection from the each of nozzles 15-1 to 15-4.F1=Pc·A1·CfF2=Pc·A2·CfF3=Pc·A3·CfF4=Pc·A4·Cf

The Pc indicates the pressure of the combustion chamber 6, and Cfindicates the thrust coefficient. A thrust force Fz along the z-axisdirection is determined by a difference between F1 and F3. A thrustforce Fy along the y-axis direction is determined by a differencebetween F2 and F4. Accelerations along the y-axis and z-axis aregenerated in the flying object, by the thrust forces Fy and Fz.

The y-axis acceleration sensor and the z-axis acceleration sensor detecta y-axis acceleration Gy and a z-axis acceleration Gz, respectively. Anobserver 32 provided in the control section 17 corrects the openingdegree command values of the divert thruster based on theseaccelerations. A storage device in the observer 32 stores an inertiamodel of the flying object. The observer 32 calculates estimated valuesof a thrust force Fye along the y-axis direction and a thrust force Fzealong the z-axis direction, based on this inertia model, the inputtedy-axis acceleration Gy and z-axis acceleration Gz.

The observer 32 transforms the opening degree commands A1c to A4c of thepintle valves into command values for the thrust forces along the y-axisdirection and the z-axis direction, based on a previously preparedformula or a table. Furthermore, the observer 32 calculates deviationsΔFy, ΔFz between these command values for the thrust forces andestimated values Fye, Fze for the thrust forces. A correction value ΔAzof a relative difference between the opening degrees of pintle valves16-1 and 16-3 of the first group is calculated so that the deviation ΔFzbecomes smaller. A correction value ΔAy of a relative difference betweenthe opening degrees of pintle valves 16-2 and 16-4 of the second groupis calculated so that the deviation ΔFy becomes smaller.

When ΔAy and ΔAz are evenly distributed to the pintle valves facing toeach other, following correction amounts are distributed to the eachpintle valve.ΔA1: +ΔAz/2ΔA2: +ΔAy/2ΔA3: −ΔAz/2ΔA4: −ΔAy/2

Furthermore, in the control method according to the present embodimentwhich is against the change of the detection value of the pressure ofthe combustion chamber 6, when the function f (opening degree command)is a proportional function, the opening degree correction values ΔA1 toΔA4 for the each of pintle valves are determined as follows.ΔA1=ΔA _(t)×(A2_(c) +A4_(c))/{2×(A1_(c) +A2_(c) +A3_(c) +A4_(c))}+ΔA_(z)/2ΔA2=ΔA _(t)×(A1_(c) +A3_(c))/{2×(A1_(c) +A2_(c) +A3_(c) +A4_(c))}+ΔA_(y)/2ΔA3=ΔA _(t)×(A2_(c) +A4_(c))/{2×(A1_(c) +A2_(c) +A3_(c) +A4_(c))}−ΔA_(z)/2ΔA4=ΔA _(t)×(A1_(c) +A3_(c))/{2×(A1_(c) +A2_(c) +A3_(c) +A4_(c))}−ΔA_(y)/2

The orbit of the flying object can be accurately controlled, by feedback control of the detection value of the acceleration about theinjection direction of the divert thruster. Moreover, control forkeeping the combustion pressure constant can be realized.

Although the present invention has described above in connection withseveral embodiments thereof, it would be apparent to those skilled inthe art that those embodiments are provided solely for illustrating thepresent invention, and should not be relied upon to construe theappended claims in a limiting sense.

What is claimed is:
 1. A method of controlling an orbit attitude,comprising: inputting opening degree command values for opening degreesof a plurality of nozzles which inject combustion gas supplied from acombustion chamber; calculating nozzle opening degree correction valuesthat are correction values for opening degree command values of theplurality of nozzles so that a deviation between a detection value of apressure of the combustion chamber and a command value of the pressurebecomes smaller; and calculating the nozzle opening degree correctionvalues for the plurality of nozzles based on the opening degree commandvalues to correct the opening degree command values by the calculatednozzle opening degree correction values, wherein a first group nozzleswhich belong to a first group of the plurality of nozzles are configuredto inject combustion gas in opposite directions along a first axis, anda second group nozzles which belong to a second group of the pluralityof nozzles are configured to inject combustion gas in oppositedirections along a second axis, wherein the calculating nozzle openingdegree correction values comprises; calculating a total correction valuethat is a correction value for a total of the opening degree commandvalues of the plurality of nozzles so that the deviation between thedetection value of the pressure and the command value of the pressurebecomes smaller; calculating a total first group value T1 that is atotal value of the opening degree command values for the first groupnozzles and a total second group value T2 that is a total value of theopening degree command values for the second group nozzles; distributingthe total correction value into a first group correction value and asecond group correction value based on a ratio of the total first groupvalue and the total second group value; and calculating the nozzleopening degree correction values for the first group nozzles so that atotal value becomes the first group correction value and calculating thenozzle opening degree correction values for the second group nozzles sothat a total value becomes the second group correction value.
 2. Themethod according to claim 1, wherein said calculating nozzle openingdegree correction values comprises: calculating the nozzle openingdegree correction values for the first group nozzles, by distributingthe first group correction value to the each of the first group nozzlesin proportion to each of the opening degree command values; andcalculating the nozzle opening degree correction values for the secondgroup nozzles, by distributing the second group correction value to theeach of the second group nozzles in proportion to each of the openingdegree command values.